Core system engineer

Thorizon is a European developer of next-generation small modular reactors (SMRs) based on molten salt technology. The company builds compact, modular nuclear reactors designed to deliver reliable baseload power and high-temperature industrial heat for sectors such as manufacturing, data centers, and energy-intensive industry. Spun off from NRG, the Netherlands' national nuclear research institute, Thorizon is commercializing molten salt reactor technology that was developed over decades of quiet research. The company aims to begin reactor construction in the early 2030s, with designs optimized for series production and flexible deployment close to end users. Thorizon's mission centers on providing clean, affordable, and safe nuclear energy without compromise. A defining feature of its technology is the use of existing nuclear waste as fuel, dramatically improving fuel efficiency and reducing the long-term waste burden of nuclear power. The company's patented cartridge system divides the reactor core into smaller, factory-produced modules, enabling off-site manufacturing, faster construction timelines, and true modular scalability. Operating at low pressure, the reactors offer an intrinsically safer profile compared to conventional nuclear designs. Thorizon has secured investment and signed a memorandum of understanding with partners including EPZ and NRG PALLAS, as well as provincial authorities, to build Europe's first commercial molten salt reactor in the Netherlands. The company has also received recognition for innovation, winning the ASML Emerging Innovator Award. By working with partners across engineering, fuel production, operations, and financing, Thorizon is positioned to scale its reactor technology to meet the growing demand for clean, dispatchable energy.

Your mission

You will be the work package lead of the nuclear core system in Thorizon Pioneer and as such responsible for all activities related to design the core in Thorizon Pioneer design and safety case. In close collaboration with internal functions – thermohydraulics, neutronics, … - you will coordinate studies you need and move the design of your system from a concept to a concrete object. Reporting to the Pioneer Project Director and Pioneer Architect, you will ensure the integration of your system within the overall reactor and manage the interface with the other systems. You will manage potential collaboration with subcontractors on design first and then on realization. In collaboration with the Safety team, you will be accountable for ensuring your system is safe and defend your case towards the regulators.

You have strong experience in system engineering and designing innovative nuclear objects with a special focus on nuclear safety. You are able to self define your weekly routine. You have a strong spirit of team effort and as such able to maneuver in cross-functional teams. You have a high level of communication skills and stakeholder management.

In this role you will:

• Define, validate and verify (functional) requirements for the nuclear core of Thorizon Pioneer, optimize the design to deliver on those requirements, and manage trade-offs in the design envelope. (e.g., reliability, performance, lifetime, costs) while continuously ensuring maximum safety and prepare for the realization of this system.
• Work in cross-functional team in Pioneer project (typically a project-based team of ~3-6 engineers from different disciplines such as nuclear engineering, core physics, thermal hydraulics, chemistry).
• Conduct engineering work for your workpackage (e.g., component and system design, computer models and analyses to simulate safety and performance). 
• Initiate projects with our expert engineers that support you with analyses, validation, verification and qualification. 
• Select, qualify and manage external contractors that support you in your mission. 
• Deliver system documentation, prepare design reviews, and ensure system integration. 
• Build documentation and presentation to enable licensing discussion with safety authorities. 
• Support program management by coordinating meetings, communicating with external partners, and leading specific projects. 
• Participate in meetings with regulators with the aim of defending in-house positions and contribute to maintaining an active dialogue with regulators (in particular ASNR, ANVS and FANC).
• Work very closely with Pioneer Architect, Functional leads and team, the program office, COO, CTO, and the rest of the teams in Lyon and Amsterdam.
• Report to the Pioneer Project Director, in the COO line.  

About you:

• Master's degree and proven working experience in nuclear design of innovative object (10 years).
• Experience with system engineering approaches is a plus.
• Knowledge and understanding of these disciplines are mandatory to succeed in the role: mechanical, neutronic, chemistry (corrosion), thermodynamic, structural.
• All-round engineer that uniquely combines content expertise, great communication and interpersonal skills: 
  • You can strategically connect the dots between design drivers in a complex multi-disciplinary project. You can zoom in and out, connecting strategy and objectives to concrete requirements, roadmaps, and actions. 
  • You are a solution-oriented go-getter who positively drives forward, 
  • You have strong stakeholder management skills and taking ownership of deliverables. 
• Excited by pioneering and a path finder for the design. You are a fast learner that has the potential to lead complex topics. 
• Excellent communicator (clear is kind) in English, both spoken and written. French and/or Dutch would be considered a strong plus. 
• Willing to travel between Lyon and Amsterdam. 
• Strong organizational and multitasking abilities, with drive for quality and accuracy.
• Inspired by an organization with a large variety of people, with different experiences and background, and have the ability to adjust your management style depending on situation and the people involved.
• Eager to learn and like challenges.

What you can expect from us:

• The opportunity to help realize the most promising reactor technology and advance Europe's energy future
• Being part of an exceptional team that combines engineering rigor, scientific excellence, and entrepreneurial drive
• Working in multidisciplinary teams on ambitious missions, with responsibility and meaningful impact from day one
• A fast-moving deep-tech environment where initiative is valued and people are trusted to make decisions
• Complex, multidisciplinary challenges that will stretch you and accelerate your growth
• Competitive compensation and participation in our employee profit-sharing plan
• An international workplace with offices in the heart of Amsterdam and Lyon